Heat the milk, coconut milk and pistachios in a heavy-based pan with the vanilla pod which is cut in two lengthways. Bring to the boil, and turn off the heat for the vanilla to infuse in the creamy milk for 5-10 minutes.
Cream together the egg yolks and sugar in a large bowl until light and fluffy. Add the powdered milk, wasabi paste and pistachio extract and mix well.
Scrape out the seeds from the vanilla pod and add to the yolk cream. Discard the pod from the warmed coconut-milk and add the food colouring.
Pour the creamy milk onto the egg mixture whisking continuously. Return the mixture to the pan on a medium heat, whisking constantly until the custard thickens and coats the back of a spoon. Set the mixture aside to cool.
Once cool, place in the fridge for 1-2 hours before pouring into an ice cream maker to churn according to your ice cream maker.